This section provides background information related to the present disclosure which is not necessarily prior art.
Circuits for detecting the amplitudes of peaks in a sinusoidal signal are known. For example, AM radio utilizes an amplitude-modulated sinusoid signal that is decoded via a peak detector. In inexpensive AM radios, the peak detector is a half wave rectifier in which a diode is used to charge a capacitor to a voltage approximating the peak. This and other conventional types of peak detectors utilize a sample and hold strategy. The problem with such a strategy is that it may not be accurate enough for certain applications, particularly in the digital domain where an analog to digital converter samples the signal. If the timing of the sample is off, for example due to a frequency shift, the result may be inaccurate for the purposes of the application.
The problem arises, for example, in digital motor controllers where commutation is controlled by an angular analog feedback sensor such as an absolute resolver. The resolver generates an amplitude-modulated sinusoidal feedback signal that carries the rotor angle. The analog feedback signal may need to be sampled in order to detect its peak levels, and it would be useful to have a peak detector that can provide relatively accurate readings of the peak timing.